1. Field of the Invention
The present invention relates to an improved construction of walk-through scaffolding.
2. Description of the Prior Art
In many industrial and construction environments scaffolding is required in locations which are accessible only through small openings, such as manholes. For example, the access openings to enter many tanks in refineries are only eighteen inches in diameter. Nevertheless, there are often tasks which must be performed in such tanks which require the use of scaffolding. For example, the interior walls of such tanks must be sandblasted, cleaned and welded at times. Although the access openings to such tanks are often extremely narrow, the tanks themselves encompass large volumes of space which require the assembly of a multiplicity of scaffolding members. The use of scaffolding is particular advantageous where lateral mobility is required. That is, the use of scaffolding allows workers to move laterally to perform necessary tasks, whereas lateral mobility is not possible when working from ladders.
At present, the types of scaffolding which are employed in locations accessible only through narrow manholes are different forms of scaffolding construction known as systems scaffolding. Systems scaffolding includes both modular scaffolding and tube and clamp scaffolding. In tube and clamp scaffolding the scaffolding framework must be built up from linear lengths of scaffolding pipe which are typically joined together by various types of locking devices and clamps. The assembly of such scaffolding within refinery tanks and other locations having limited access openings requires tools for tightening the clamps and considerable manual manipulation to properly position and tighten each clamp at each joint. Easily fifty to seventy five percent of the total time spent in accomplishing a project within such tanks, such as sandblasting, cleaning and welding, is consumed in the erection and disassembly of the scaffolding used for these tasks.
A different type of scaffolding is employed in other environments where no narrow access manholes are involved. A very popular type of scaffolding which is widely utilized in locations without narrow access opening limitations is a type of scaffolding known as frame scaffolding, one popular form of which is termed walk-through scaffolding. The individual frames of walk-through frame scaffolding, hereinafter referred to as walk-through scaffolding, are of a generally arch-like configuration formed by outer, generally vertical legs joined together at their tops by a crosspiece and including braces which normally extend upwardly and inwardly to interior locations on the crosspiece from the outer, vertically oriented pipes forming the legs. The braces, the vertically oriented pipes, and the crosspieces of each frame are all normally welded together and each walk-through frame is positioned as a rigid unit. The frames are disposed in vertical planes and are joined together by laterally extending crossbraces which extend between the laterally separated and generally vertically oriented scaffolding frames. Successive levels of the frames are vertically stacked, one atop another, to the height necessary to accommodate workers at the elevations above grade at which the tasks are to be performed.
Walk-through scaffolding is widely used in the construction industry and is erected around a building under construction to allow construction workers to reach the upper levels of the building. Walk-through scaffolding is also used in many industrial maintenance repair operations where tasks are to be performed at elevations above the surface and where there significant space restrictions do not exist.
Walk-through scaffolding is far easier and quicker to assemble and disassemble than is either modular or tube and clamp scaffolding. The large walk-through scaffolding frame sections can be interconnected by crossbraces. The ends of the crossbraces terminate in locking devices which require no tools for engagement to achieve locking interconnection. Typical locking devices of this type are a plow bolt with a wing nut, a snap-on latch, and drop lock and flip lock connectors. Since no tools are required for the assembly and disassembly of walk-through scaffolding, such scaffolding can be put into place and disassembled relatively quickly.
The assembly and disassembly of modular and tube and clamp scaffolding, on the other hand, requires the interconnection of scaffold members by means of clamps, such as swivel clamps and right angle clamps, which require bolts to be tightened with wrenches or other tools at each and every joint throughout the scaffolding structure. The laborious process of tightening or loosening one or more bolts at each interconnection of modular linear scaffolding members greatly lengthens both the time of assembly and the time of disassembly. As a result, the cost of erecting and disassembling modular scaffolding is increased enormously. Nevertheless, modular scaffolding has heretofore been the only practical, commercially available type of scaffolding which could be used within enclosures accessible only through narrow manholes or access openings, since the large frame elements of walk-through scaffolding cannot pass through such openings.